The overall aim of the proposal is to identify molecules of functional importance in the activation of macrophages, particularly in regard to tumor cell killing. Macrophage activation is a critical part of the immune response and as such, the study of macrophage activation is of potential importance for understanding and treating neoplastic, infectious and immunologically related disorders. Differential screening of a cDNA library has identified 2 mRNA species of increased abundance in macrophages following exposure to gamma interferon as well as other activators. One of these mRNA species (designated 20-2), its gene, and protein product, have been chosen for further study. The specific aims of the proposal are: to isolate and sequence a full-length cDNA clone of 20-2 in part to understand the function of the predicted protein product; to characterize the 20-2 mRNA in terms of its dose response to specific inducers, its time course of accumulation following induction, and its tissue and cell type distribution; to raise antisera to the 20-2 protein product predicted from the cDNA clone using synthetic peptides and fusion proteins in order to identify and assay for the 20-2 protein, determine its tissue and cellular location and determine the effects of antisera in assays of macrophage-mediated cytotoxicity; to use the 20-2 cDNA clone to isolate corresponding genomic clones in order to identify elements important in the regulation of 20-2 gene expression; to prepare the 20-2 protein by using an expression system, for physical, biochemical and functional studies. The specific aims are directed at achieving the overall goal of understanding the molecular mechanisms of macrophage activation in order to control and exploit this system for the treatment of human disease.